There are two kinds of the prior art roller type material racks. The first kind comprises a roller pivoted horizontally to a fastening mount for holding a square material or a platelike material. The second kind comprises two rollers which are fastened in a V-shaped manner for holding a round material having certain outer diameters. It is a well-known fact that process materials have different shapes and sizes. The materials having a sector cross section or a triangular cross section can not be held on the prior art roller type racks described above. In addition, the round materials have different outer diameters. As a result, the V-shaped roller type racks having different open angles must be used to hold various round materials. It is often inconvenient for an operator to change the racks to suit the shapes and the sizes of the materials to be processed.